# Elliptic point

From Diffgeom

Template:Point property on regular surface

## Contents

## Definition

A point on a regular surface is termed an elliptic point if it satisfies the following equivalent conditions:

- Both its principal curvatures have the same sign
- Its Gaussian curvature is positive

## Relation with other properties

### Stronger properties

- Umbilic point (except when its flat at the point)